Adds feature for failure to link AppDelegate
Replaces ; with && in system_or_exit to have good exit codes
Enables visibility of symbols in Release object files
Merge pull request #91 from dracco/no-appdelegate-reference

- Fix bundle Rakefile failing with Undefined symbols
- Rakefile returns correct exit code
- Project used under tests doesn't hide symbols when built in Release configuration
- Projects will still have to manually toggle this build setting in for their application 
  target in order for specs to be run from command line in Release.